1. Field of The Invention
The present invention relates to an adjustable cap unit for a mine support frame, particularly for a shield-type support frame. The adjustable cap unit includes a main cap and an adjustable cap hinged to the main cap by means of a hinge connection provided on the roof side of the caps. The adjustable cap unit further includes an adjusting cylinder which is hinged to the adjustable cap and to the main cap and is located underneath the hinge connection within the width of the adjusting cap and main cap.
2. Description of the Prior art
Adjustable caps of the type described are used, for example, where the hanging roof is to be upheld as early as possible immediately next to the working face with a positive pressure. For that purpose, the adjustable caps are connected to the main caps by means of hinged axles extending in the longwall direction. The hinge axles are generally provided slightly underneath the upper sides of the caps. The positive pressure at the front end of an adjustable cap is obtained by means of at least one hydraulically operated adjusting cylinder which extends across the hinge connection and is hinged to the adjustable cap and the main cap.
As long as the available seam thickness permits a sufficient clearance for travel underneath the caps, it is usually not difficult to provide an adjusting cylinder underneath the caps. However, if the adjusting cylinder is to be arranged within the caps, these caps must have a minimum thickness, particularly in the region of the hinge connection, in order to accommodate an adjusting cylinder which is capable of providing the necessary pressure at the front end of the cap (Brochure 6.81 of Firma Hermann Hemscheidt Maschinenfabrik GmbG & Co. "Schildausbautyp G 320 - 12/27 fur mittlere Floze" [Shield-type support model G 320 - 12/27 for medium-sized seams]). In the case of small seam thicknesses, a unit of the type described above can not be used because the thickness of the cap makes it generally not possible to ensure the minimum permissible travel clearance of 400 mm. It must be further taken into consideration in these cases that the clearance between the bottom sides of the caps and the upper sides of structure located on the backfill side of the support conveyor, such as, spill plates, is not large enough to permit observation from the travel area of the conveyor, the extraction machine and the working face in a manner which is acceptable with respect to safety requirements.
It is, therefore, the primary object of the present invention to improve the adjustable cap unit of the type described above, so that, even in the case of extremely small seam thicknesses of as little as about 500 mm, a minimum clearance of 400 mm is ensured while particularly the adjustable cap has sufficient stiffness with respect to bending and twisting and the adjustable cap can exert the necessary positive contact pressure at the front end of the cap.